The term partial discharges is intended to indicate an undesired recombination of electric charges occurring in the dielectric (insulating) material of electric components, when the latter have defects of various types. Here, a pulse current is generated in portions of dielectric material, and causes an electromagnetic wave to propagate through the power or ground cables of the relevant electric system, and radiate through the various media through which this wave passes (dielectric Material, metals, air, etc.).
Partial discharges are usually measured by detecting the signals generated by such discharges using special sensors and analyzing such signals by suitable software. These sensors usually detect the discharges due to their propagation by conduction; therefore, they shall be fitted onto the cables or placed in the proximity of the components being measured, and often require temporary system shutdown. Such sensors include: dipole or dipole array antennas, “Rogowsky” or “coupler transformer” type magnetic sensors; electric or magnetic field proximity sensors, operating a few centimeters from the source; acoustic or piezoelectric sensors. All of these sensors are characterized by high performances in particular situations, but are not flexible enough to be used in any condition. An additional drawback is that the use of such sensors requires direct or mediated connection to the mains for assessment of the operating voltage phase at the discharge.
Prior art technology for radiated noise detection, which does not require direct connection to the system, includes electric or magnetic field sensors that utilize the principle of resonance for picking up signals of the highest amplitude, even without requiring any amplifier. The drawback of this kind of sensors consists in their signal processing difficulties, caused by resonance, concerning the form of acquired pulses.
Therefore, the need is felt for a partial discharge detection device that can overcome the above drawbacks.